Much of the world's electrical power is generated from the combustion of fossil-fuels such as coal, natural gas and fuel oil. Carbon dioxide (CO2) is a by-product of combustion and is the principal greenhouse gas. As such, CO2 emissions are believed to be a major contributor to the phenomenon of global warming, which could lead to drastic climate changes (e.g., violent weather patterns, changes in precipitation, rising ocean levels, and increases in temperature). Additionally, because CO2 is an acidic gas, it forms the corrosive product carbonic acid in the presence of water.
Several approaches for extraction CO2 have been suggested, including transformation by algae, sequestration in oceans, storage in depleted oil and natural gas wells, dissolution in deep water tables, and transformation into carbonates. However, many of these approaches have significant draw backs, and are often economically or ecologically unviable.
Carbonic anhydrases (EC 4.2.1.1; and CAS No. 9001-03-0) catalyze the inter-conversion between carbon dioxide and bicarbonate [CO2+H2OHCO3−+H+]. The active site of most carbonic anhydrases contains a zinc ion, therefore; these enzymes are also classified as metalloenzymes. Carbonic anhydrases may serve as biological catalysts to accelerate the capture of CO2. Naturally occurring carbonic anhydrases typically function at low temperatures and are poorly suited to extraction of CO2 from hot combustion gases. Accordingly, the need exists for carbonic anhydrases that can effectively hydrate CO2 under inhospitable conditions (e.g., elevated temperatures, alkaline pH, and/or in the presence of high concentrations of bicarbonate).